DC/DC CONVERTER AND POWER SOURCE DEVICE

Description

TECHNICAL FIELD The present invention relates to a DC/DC converter and a power source device.

BACKGROUND ART

In recent years, as the battery capacity of electric vehicles increases, the charge capacity of quick chargers for electric vehicles having a large capacity such as 200 [kW] is increasing from conventional several 10 [kW]. Thus, it is more important to reduce the size, increase the efficiency, and reduce the cost of the power source device used in the quick charger.

The power source device of a quick charger includes a power supply unit including an AC/DC converter and a DC/DC converter. Conventionally, a voltage current type DC/DC converter has been used as the DC/DC converter, but in recent years, a current resonant type DC/DC converter of an LLC method, a CLLC method, or the like is capable of being reduced in size, having high efficiency, and having low cost by improving control techniques is used in view of the background. The current resonant type DC/DC converter needs to be controlled by changing a driving frequency over a wide range by input voltage, output voltage, and output current.

The CHAdeMO standard, which is a charging standard for electric vehicles, defines ripple noise of a quick charger as, for example, equal to or less than 10 [Hz] /less than 1.5 [App] and equal to or less than 5 [Hz]/less than 3 [App]. In the case of the current resonant type DC/DC converter, ripple noise (input voltage ripple) included in the input voltage is propagated from a primary-side switching circuit to a secondary-side rectifier circuit via a high-frequency isolation transformer, and is output as ripple noise (output current ripple) included in the output current. The output current ripple adversely affects the battery of the electric vehicle, and thus, in general, a power line noise filter circuit (hereinafter, the filter circuit) is provided between the DC/DC converter and the preceding AC/DC converter (or in the AC/DC converter) to reduce the output current ripple by reducing the input voltage ripple.

In order to reduce the size and cost of the filter circuit, it is necessary to increase the cutoff frequency of the filter circuit. However, when the cutoff frequency of the filter circuit is increased, a low frequency component of ripple noise flows out from the filter circuit. When an AC power supply connected to the AC end side of the AC/DC converter is a three-phase AC of 50 [Hz] or 60 [Hz], for example, a harmonic current (AC ripple) of 300 [Hz] or 360 [Hz], which is the sixth harmonic of the AC current input from the AC power supply, flows out of the filter circuit. When the AC power supply is a single-phase AC of 50 [Hz] or 60 [Hz], for example, a lower-order harmonic current (AC ripple) of 100 [Hz] or 120 [Hz], which is a second-order low harmonic of the AC current input from the AC power supply, flows out of the filter circuit.

On the other hand, when the cutoff frequency of the filter circuit is lowered, a low frequency component of ripple noise can be reduced, but this leads to an increase in size of the choke coil and an increase in capacity of the electrolytic capacitor that constituting the filter circuit. As a result, the filter circuit and the power source device are increased in size and cost. Specifically, in the case of a single-phase AC power supply, when it is intended to cope with a second-order low AC ripple, it is necessary to set a lower cutoff frequency, which leads to an increase in size of the filter circuit.

Accordingly, in the current resonant type DC/DC converter described in Patent Document 1, the control unit is provided with an input voltage ripple extraction unit that extracts an input voltage ripple and a gain generation unit that generates a gain so that the output current ripple becomes equal to or less than a certain value. The current resonant type DC/DC converter described in Patent Document 1 performs feedforward control by the input voltage ripple multiplied by the gain, and thus the output current ripple can be reduced even if the cutoff frequency of the filter circuit is increased.

Further, the LLC converter described in Patent Document 2 reduces the output current ripple by adjusting the driving frequency on the basis of a feedforward signal generated by the difference between the input voltage and the average input voltage and the feedback signal of the output current.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: Japanese Patent Application No. 2021-172421

Patent Document 2: CN-B-113346774

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In the current resonant type DC/DC converter described in Patent Document 1, in a case where the feedforward control is overcontrolled, the overcontrol cannot be detected and suppressed, and thus there arises a problem that the output current ripple cannot be reduced. Specifically, in the quick charger, the battery voltage of the electric vehicle greatly changes from 150 [V] to 450 [V], and thus may be controlled by changing the input voltage of the current resonant type DC/DC converter, and a regulation value of the current ripple also changes depending on the current value, resulting in overcontrol depending on the operation state and causing the above-described problem. Even in the LLC converter described in Patent Document 2, when the correction gain of the feedforward control is increased, the feedforward control is overcontrolled, and in that case, a problem similar to that of the current resonant type DC/DC converter described in Patent Document 1 occurs.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a DC/DC converter and a power source device capable of reducing an output ripple even when overcontrol occurs.

Means for Solving the Problems

In order to solve the problems, a DC/DC converter according to the present invention includes:

• • a power unit that includes a drive circuit including a switching element and a rectifier circuit, switches an input voltage by the switching element, and rectifies the input voltage by the rectifier circuit to obtain a DC output; and
  • a control unit that controls the drive circuit, in which
  • the control unit includes:
  • a first control unit that generates a first control command value for bringing the output close to a target value;
  • an input voltage ripple extraction unit that extracts an input voltage ripple included in the input voltage;
  • an output ripple extraction unit that extracts an output ripple included in the output;
  • a second control unit that calculates an output ripple with polarity by multiplying the output ripple by a value including polarity of the input voltage ripple, generates a gain for bringing the output ripple with polarity close to a ripple target value, and generates a second control command value by multiplying the input voltage ripple by the gain; and
  • a switching control unit that performs feedforward control of the drive circuit on the basis of the first control command value and the second control command value.

In this configuration, since the second control unit generates the gain on the basis of the output ripple with polarity, the polarity of the gain is reversed between a case of overcontrol and a case of non-overcontrol (case of normal control). Since the switching control unit performs feedforward control of the drive circuit on the basis of the second control command value obtained by multiplying the input voltage ripple by the gain, overcontrol is suppressed, and the output ripple can be reduced. Further, in this configuration, it is possible to perform control processing similar to that at the time of normal control to suppress overcontrol.

The DC/DC converter can be configured in such a manner that

• • the second control unit includes a polarity determination unit, and
  • the polarity determination unit outputs a value of +1 when the input voltage ripple is positive and outputs a value of −1 when the input voltage ripple is negative as the value including the polarity.

The DC/DC converter can be configured in such a manner that

• • the second control unit includes a gain-added polarity determination unit, and
  • the gain-added polarity determination unit outputs the input voltage ripple subjected to gain adjustment as the value including the polarity.

The DC/DC converter can be configured in such a manner that

• • the second control unit includes:
  • a first multiplier that calculates the output ripple with polarity;
  • a calculation unit that calculates a difference between the output ripple with polarity and the ripple target value;
  • a PI control unit that generates the gain on a basis of the difference; and
  • a second multiplier that multiplies the input voltage ripple by the gain.

The DC/DC converter can be configured in such a manner that

• • the PI control unit changes a magnitude of a PI gain according to the input voltage.

The DC/DC converter can be configured in such a manner that

• • the output ripple extraction unit extracts an output current ripple or an output voltage ripple included in the output as the output ripple.

The DC/DC converter can be configured in such a manner that

• • the input voltage ripple extraction unit extracts the input voltage ripples of an N number of frequencies (N is an integer equal to or more than 2),
  • the output ripple extraction unit extracts the output ripples of the N number of frequencies,
  • the second control unit generates the N number of the second control command values on a basis of the input voltage ripples of the N number of frequencies and the output ripples of the N number of frequencies, and
  • the switching control unit performs feedforward control on the drive circuit on a basis of the first control command value and the N number of the second control command values.

In order to solve the problems, a power source device according to the present invention includes:

• • an AC/DC converter; and
  • any one of the DC/DC converters described above connected to a DC end of the AC/DC converter.

In the power source device, preferably,

• • an output voltage of the AC/DC converter is changed according to an output voltage of the DC/DC converter.

Effect of the Invention

According to the present invention, it is possible to provide a DC/DC converter and a power source device capable of reducing an output ripple even when overcontrol occurs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of a DC/DC converter and a power source device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example (in a case of normal control) of a waveform of each unit in a control unit of the DC/DC converter according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an example (in a case of overcontrol) of a waveform of each unit in a control unit of the DC/DC converter according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating an example of a DC/DC converter and a power source device according to a second embodiment of the present invention.

FIG. 5 is a block diagram illustrating an example of a control unit of the DC/DC converter according to the second embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of a DC/DC converter and a power source device according to the present invention will be described with reference to the accompanying drawings.

First Embodiment

FIG. 1 illustrates a power source device 1 according to a first embodiment of the present invention. The power source device 1 includes an AC/DC converter 10 and a current resonant type DC/DC converter 20 (a power unit 21 and a control unit 22) according to the first embodiment of the present invention.

The AC/DC converter 10 includes an AC end and a DC end, the AC end is connected to the AC power supply 2 (for example, a three-phase AC output commercial power supply), and the DC end is connected to the power unit 21 of the DC/DC converter 20. Further, the AC/DC converter 10 includes a power conversion unit including at least one switching element, a control unit that controls the power conversion unit, and a power line noise filter circuit (hereinafter, the filter circuit). The AC/DC converter 10 converts AC power input from the AC power supply 2 into DC power by an AC/DC conversion operation of the power conversion unit, and outputs the DC power to the power unit 21 of the DC/DC converter 20 via a filter circuit. The control unit controls the output voltage by, for example, constant voltage control. The power conversion unit may have a power factor correction (PFC) function.

The filter circuit of the AC/DC converter 10 is, for example, an LC filter circuit including a choke coil and a capacitor (an electrolytic capacitor or a film capacitor). In the filter circuit of the present embodiment, the cutoff frequency is set to a relatively high value in order to reduce the size and cost of the filter circuit. Thus, the filter circuit blocks most of switching noise and switching ripple generated in synchronization with the switching frequency of the switching element of the AC/DC converter 10. On the other hand, in this filter circuit, the AC ripple generated in synchronization with the frequency (50 [Hz] or 60 [Hz]) of the AC power supply 2 passes through. Thus, a constant voltage output of the AC/DC converter 10, that is, an input voltage of the DC/DC converter 20 includes an input voltage ripple generated in synchronization with the frequency of the AC power supply 2. Note that a part of the filter circuit may be provided between the AC/DC converter 10 and the DC/DC converter 20 or at an input unit of the DC/DC converter 20.

The power unit 21 of the DC/DC converter 20 includes terminals T1 to T4, the terminals T1 and T2 are connected to the AC/DC converter 10, and the terminals T3 and T4 are connected to the storage battery 3 (for example, a lithium-ion battery of an electric vehicle) as a load. Further, the power unit 21 includes a primary-side switching circuit 21a, a resonance circuit 21b, an isolation transformer 21c, and a secondary-side rectifier circuit 21d. The power unit 21 generates a desired direct current (charging current) on the basis of a direct current input voltage input from the AC/DC converter 10, and supplies the direct current to the storage battery 3. Note that the load is not limited to the storage battery 3.

The primary-side switching circuit 21a is a drive circuit including at least one switching element, and is, for example, a full bridge circuit, a three-phase bridge circuit, or a half bridge circuit. As the switching element, for example, a power semiconductor such as an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET) can be used. A diode (including a built-in diode) may be connected in parallel in the reverse direction, and a capacitor (including a parasitic capacitance) may be connected in parallel to the current path of the switching element.

The resonance circuit 21b is an LC resonance circuit including a resonance coil (inductance) and a resonance capacitor (capacitance). The resonance circuit 21b constitutes an LLC resonance circuit together with an excitation coil (inductance) and a primary-side coil of the isolation transformer 21c. Note that the resonance coil may include only a leakage inductance due to leakage magnetic flux of the isolation transformer 21c, or may include a leakage inductance due to leakage magnetic flux of the isolation transformer 21c and an individual coil.

The isolation transformer 21c is a high-frequency isolation transformer including a primary-side coil (primary winding) and a secondary-side coil (secondary winding). The primary-side coil is connected to the primary-side switching circuit 21a via the resonance circuit 21b, and the secondary-side coil is connected to the secondary-side rectifier circuit 21d. The isolation transformer 21c includes one or a plurality of high-frequency isolation transformers.

The secondary-side rectifier circuit 21d includes a diode rectifier circuit including a plurality of diodes or a synchronous rectifier circuit including a plurality of switching elements including a plurality of power semiconductors, and a smoothing circuit including a capacitor.

The control unit 22 of the DC/DC converter 20 includes a first control unit 23, an input voltage ripple extraction unit 24, an output current ripple extraction unit 25, a second control unit 26, and a switching control unit 27. Each of the units 23 to 27 of the control unit 22 may include an analog circuit, a digital circuit including a microcontroller, a DSP, or the like, or a circuit combining an analog circuit and a digital circuit. Furthermore, the control unit 22 may also serve as a control unit of the AC/DC converter 10.

Note that various signals are input and output between the units 23 to 27 of the control unit 22, but in the following description, the term “signal” is omitted from the signal names of the various signals. For example, a “signal related to a current value” is simply expressed as a “current value”, and a “difference signal” is simply expressed as a “difference”. The same applies to the second embodiment described later.

The first control unit 23 includes an output current detection unit 23a, a calculation unit 23b, and a PI control unit 23c. The output current detection unit 23a detects an output current of the DC/DC converter 20 output from the secondary-side rectifier circuit 21d, and outputs a current value of the output current to the calculation unit 23b. The calculation unit 23b calculates a difference between the current value of the output current and a target value (command value) of an output current input from an external device, and outputs the difference to the PI control unit 23c. The PI control unit 23c performs proportional integral (PI) calculation based on the difference, and generates a first control command value CC for causing the current value of the output current to approach the target value.

The input voltage ripple extraction unit 24 detects an input voltage of the DC/DC converter 20 input to the primary-side switching circuit 21a, and extracts ripple noise (hereinafter, an input voltage ripple) included in the input voltage. The input voltage ripple includes switching noise, switching ripple, and AC ripple as described above. The input voltage ripple extraction unit 24 includes a filter for extracting the input voltage ripple, for example, a band pass filter (BPF) obtained by combining a low pass filter (LPF) and a high pass filter (HPF). The input voltage ripple extraction unit 24 outputs the voltage value (hereinafter, a ripple voltage value VR) of the extracted input voltage ripple to the second control unit 26.

The output current ripple extraction unit 25 extracts ripple noise (hereinafter, an output current ripple) included in the output current detected by the output current detection unit 23a. Similarly to the input voltage ripple extraction unit 24, the output current ripple extraction unit 25 includes, for example, a band pass filter (BPF) obtained by combining a low pass filter (LPF) and a high pass filter (HPF). The output current ripple extraction unit 25 outputs a current value of the extracted output current ripple (hereinafter, a ripple current value IR) to the second control unit 26.

The second control unit 26 includes a polarity determination unit 26a, a first multiplier 26b, a calculation unit 26c, a PI control unit 26d, and a second multiplier 26e.

The polarity determination unit 26a determines the polarity of the ripple voltage value VR and outputs a sign F of the polarity. The sign F has a positive (in the present embodiment, +1) or negative (in the present embodiment, −1) value. That is, the polarity determination unit 26a outputs the sign F having a value of +1 when the ripple voltage value VR is positive, and outputs the sign F having a value of −1 when the ripple voltage value VR is negative.

The first multiplier 26b calculates a ripple current value with polarity FIR by multiplying the ripple current value IR input from the output current ripple extraction unit 25 by the sign F input from the polarity determination unit 26a. The first multiplier 26b outputs a ripple current value with polarity FIR, which is a product of the ripple current value IR and the sign F, to the calculation unit 26c.

The calculation unit 26c calculates a difference between the ripple current value with polarity FIR input from the first multiplier 26b and a ripple target value set in advance, and outputs the difference to the PI control unit 26d. The ripple target value is a target value of a peak-to-peak current value of the output current ripple, and is set to 0 [App] in the present embodiment.

The PI control unit 26d performs proportional integral (PI) calculation based on the difference between the ripple current value with polarity FIR and the ripple target value, and generates a gain G for causing the ripple current value with polarity FIR to approach the target value. The PI control unit 26d also functions as a smoothing filter for rectification.

The second multiplier 26e multiplies the ripple voltage value VR input from the input voltage ripple extraction unit 24 by the gain G input from the PI control unit 26d to generate a second control command value FG that is a product of the ripple voltage value VR and the gain G.

The switching control unit 27 includes a calculation unit 27a and a pulse generation unit 27b. The switching control unit 27 performs feedforward control on the first control command value CC for bringing the output current value close to the target value using the second control command value FG that is the product of the ripple voltage value VR and the gain G. Specifically, the calculation unit 27a adds the first control command value CC input from the PI control unit 23c and the second control command value FG input from the second multiplier 26e, and outputs the addition value to the pulse generation unit 27b. The pulse generation unit 27b determines the driving frequency of the switching element of the primary-side switching circuit 21a on the basis of the addition value of the first control command value CC and the second control command value FG, and generates a switching pulse for turning on/off the switching element at the driving frequency.

That is, the pulse generation unit 27b performs frequency modulation control on the primary-side switching circuit 21a. When the switching element of the primary-side switching circuit 21a is turned on/off according to the frequency modulation control, a resonance current flows to the primary-side coil of the isolation transformer 21c via the resonance circuit 21b. Note that, at the time of low output, the pulse generation unit 27b may perform control such as burst (intermittent) control or phase shift control on the primary-side switching circuit 21a. When the secondary-side rectifier circuit 21d includes a synchronous rectifier circuit, the pulse generation unit 27b acquires information necessary for synchronous rectification control from the power unit 21, generates a switching pulse for turning on/off the switching element of the secondary-side rectifier circuit 21d in synchronization with the resonance current, and performs the synchronous rectification control of the secondary-side rectifier circuit 21d. In addition, at the time of high output, the pulse generation unit 27b may short-circuit the secondary-side rectifier circuit 21d by turning on some switching elements of the secondary-side rectifier circuit 21d in synchronization with the primary-side switching circuit 21a, and perform boost control.

Next, the operation of the DC/DC converter 20 will be described in more detail with reference to FIGS. 2 and 3. FIG. 2 is a diagram illustrating an example of waveforms of each unit in the control unit 22 at the time of normal control in which the feedforward control is not overcontrolled. FIG. 3 is a diagram illustrating an example of waveforms of each unit in the control unit 22 at the time of overcontrol in which the feedforward control is overcontrolled. In the following description, the input voltage ripple is a sine wave in order to simplify the description, but the input voltage ripple may have an irregular waveform other than the sine wave, and in this case, the operation also corresponds to the irregular waveform.

In the case of the normal control, from time t1 to time t3 in FIG. 2, the ripple voltage value VR of the input voltage ripple extracted by the input voltage ripple extraction unit 24 is an instantaneous value of a sine wave for one cycle from 0° to 360° (FIG. 2(A)). The sign F of the polarity determination unit 26a is a value of +1 from time t1 to time t2 because the ripple voltage value VR is positive, and is a value of −1 from time t2 to time t3 because the ripple voltage value VR is negative (FIG. 2(B)).

Since the output current ripple due to the input voltage ripple occurs in the DC/DC converter 20, from time t1 to time t3, the ripple current value IR of the output current ripple extracted by the output current ripple extraction unit 25 becomes an instantaneous value of a sine wave for one cycle from 0° to 360°, similarly to the ripple voltage value VR (FIG. 2(C)).

The ripple current value with polarity FIR has a positive waveform from time t1 to time t2 since the sign F is +1 and the ripple current value IR is positive, and has a positive waveform from time t2 to time t3 since the sign F is −1 and the ripple current value IR is negative (FIG. 2(D)). Furthermore, since the ripple target value is 0 in the present embodiment, the ripple current value with polarity FIR is input as a positive waveform as it is to the PI control unit 26d.

The PI control unit 26d obtains a positive gain G obtained by smoothing the ripple current value with polarity FIR having a positive waveform from time t1 to time t3 (FIG. 2(E)). As a result, the second control command value FG, which is the product of the ripple voltage value VR and the gain G, has a waveform having the same polarity as the ripple voltage value VR (FIG. 2(F)).

Thus, in the case of normal control, the control unit 22 performs the feedforward control based on the second control command value FG together with the feedback control based on the first control command value CC, and thereby can perform output current ripple correction and reduce the output current ripple.

In the case of overcontrol in which the feedforward control is overcontrolled, from time t1 to time t3 in FIG. 3, the ripple voltage value VR and the sign F have waveforms similar to those in the normal control (FIGS. 3(A) and 3(B)). On the other hand, the ripple current value IR of the output current ripple has a waveform with a polarity opposite to that of the ripple voltage value VR due to the excessive feedforward control amount due to the overcontrol (FIG. 3(C)). That is, the ripple current value IR has a negative waveform when the ripple voltage value VR from time t1 to time t2 is positive, and has a positive waveform when the ripple voltage value VR from time t2 to time t3 is negative.

As a result, the ripple current value with polarity FIR at the time of overcontrol has a negative waveform from time t1 to time t2 because the sign F is +1 and the ripple current value IR is negative, and likewise has a negative waveform from time t2 to time t3 since the sign F is −1 and the ripple current value IR is positive (FIG. 3(D)). The ripple current value with polarity FIR is input as a negative waveform to the PI control unit 26d.

The PI control unit 26d obtains a negative gain G obtained by smoothing the ripple current value with polarity FIR having a negative waveform from time t1 to time t3 (FIG. 3(E)). As described above, since the gain G at the time of overcontrol has a polarity opposite to that of the gain G at the time of normal control and has a negative value, the second control command value FG, which is a product of the ripple voltage value VR and the gain G, has a waveform having a polarity opposite to that of the ripple voltage value VR (FIG. 3(F)). That is, the second control command value FG has a negative waveform from time t1 to time t2 and a positive waveform from time t2 to time t3.

Thus, even at the time of overcontrol, the control unit 22 performs the feedforward control based on the second control command value FG together with the feedback control based on the first control command value CC, and thereby can suppress the overcontrol of the feedforward control and reduce the output current ripple.

As described above, the DC/DC converter 20 can suppress the overcontrol of the feedforward control by performing the control processing similar to that at the time of the normal control even at the time of the overcontrol, so that a special configuration for detecting the overcontrol is unnecessary, and a special control processing for suppressing the overcontrol is also unnecessary. Furthermore, the DC/DC converter 20 can stably perform control even when the correction gain by feedforward (PI gain of the PI control unit 26d) is increased, and can appropriately reduce the output current ripple due to the input voltage ripple. In addition, according to the present control method, even in a case where the input voltage ripple waveform and the output current ripple waveform are out of phase, the same control as in the overcontrol can be performed, so that the control can be stably performed without the overcontrol due to the phase shift.

Note that the power source device 1 may change the input voltage of the DC/DC converter 20 (the output voltage of the AC/DC converter 10) according to the output voltage of DC/DC converter 20. Preferably, the input voltage is decreased when the output voltage of the DC/DC converter 20 is small, and the input voltage is increased when the output voltage of the DC/DC converter 20 is large.

When the input voltage is increased, the output current ripple due to the input voltage ripple is also increased, and thus it is preferable that the correction gain by feedforward (PI gain of the PI control unit 26d) is large. On the other hand, when the input voltage is decreased, the output current ripple due to the input voltage ripple is also decreased, and thus, when the correction gain is large, the possibility that the feedforward control is overcontrolled is increased. Accordingly, the DC/DC converter 20 preferably changes the correction gain according to the input voltage. For example, the DC/DC converter 20 may change the magnitude of the correction gain so that the correction gain increases when the input voltage is large and the correction gain decreases when the input voltage is small.

Second Embodiment

FIG. 4 illustrates a power source device 1′ according to a second embodiment of the present invention. As illustrated in FIG. 4, the power source device 1′ includes an AC/DC converter 10 and a current resonant type DC/DC converter 20′ according to the second embodiment of the present invention. The power source device 1′ has the same configuration as the power source device 1 (FIG. 1) of the first embodiment except for a DC/DC converter 20′.

The DC/DC converter 20′ includes a power unit 21 and a control unit 22′. The DC/DC converter 20′ has the same configuration as the DC/DC converter 20 (FIG. 1) of the first embodiment except for the control unit 22′.

As illustrated in FIG. 5, the control unit 22′ includes a first control unit 23, an input voltage ripple extraction unit 24′ (24K, 24L, and 24M), an output current ripple extraction unit 25′ (25K, 25L, and 25M), a second control unit 26′ (26K, 26L, and 26M), and a switching control unit 27.

In the control unit 22′, the first control unit 23 (an output current detection unit 23a, a calculation unit 23b, and a PI control unit 23c) and the switching control unit 27 (the calculation unit 27a and the pulse generation unit 27b) have the same configuration as that of the first embodiment, and the input voltage ripple extraction unit 24′ (24K, 24L, and 24M), the output current ripple extraction unit 25′ (25K, 25L, and 25M), and the second control unit 26′ (26K, 26L, and 26M) have different configurations from those of the first embodiment. Due to this difference in configuration, the control unit 22′ corresponds to ripple noise with three different frequencies (in the present embodiment, Kth order, Lth order, and Mth order are used).

The input voltage ripple extraction unit 24K extracts ripple noise (hereinafter, the input voltage ripple) of the Kth order frequency included in the input voltage. The input voltage ripple extraction unit 24K includes a filter for extracting the input voltage ripple, for example, a band pass filter (BPF) obtained by combining a low pass filter (LPF) and a high pass filter (HPF). The input voltage ripple extraction unit 24K outputs a voltage value (ripple voltage value VR_K) of the extracted Kth order input voltage ripple to the second control unit 26K.

Similarly, the input voltage ripple extraction unit 24L extracts the input voltage ripple of the Lth order frequency included in the input voltage, and outputs a voltage value (ripple voltage value VR_L) of the extracted Lth input voltage ripple to the second control unit 26L. Further, the input voltage ripple extraction unit 24M extracts the input voltage ripple of the Mth order frequency included in the input voltage, and outputs a voltage value (ripple voltage value VR_M) of the extracted Mth order input voltage ripple to the second control unit 26M. As described above, the input voltage ripple extraction unit 24′ is common to the input voltage ripple extraction unit 24 of the first embodiment except that it corresponds to the Kth, Lth, and Mth order frequencies.

The output current ripple extraction unit 25K extracts ripple noise (hereinafter, the output current ripple) of the Kth order frequency included in the output current detected by the output current detection unit 23a. The output current ripple extraction unit 25K includes, for example, a band pass filter (BPF) obtained by combining a low pass filter (LPF) and a high pass filter (HPF). The output current ripple extraction unit 25K outputs a current value (ripple current value IR_K) of the extracted Kth order output current ripple to the second control unit 26K.

Similarly, the output current ripple extraction unit 25L extracts an output

current ripple of an Lth order frequency included in the output current detected by the output current detection unit 23a, and outputs a current value (ripple current value IR_L) of the extracted Lth output current ripple to the second control unit 26L. Further, the output current ripple extraction unit 25M extracts the output current ripple of the Mth order frequency included in the output current detected by the output current detection unit 23a, and outputs a current value (ripple current value IR_M) of the extracted Mth order output current ripple to the second control unit 26M. As described above, the output current ripple extraction unit 25′ is common to the output current ripple extraction unit 25 of the first embodiment except that it corresponds to the Kth, Lth, and Mth order frequencies.

Each of the second control units 26K, 26L, and 26M includes a polarity determination unit 26a, a first multiplier 26b, a calculation unit 26c, a PI control unit 26d, and a second multiplier 26e. The second control unit 26′ is common to the second control unit 26 of the first embodiment except that it corresponds to the Kth, Lth, and Mth order frequencies. Each of the polarity determination unit 26a, the first multiplier 26b, the calculation unit 26c, the PI control unit 26d, and the second multiplier 26e has the same configuration as that of the first embodiment.

For example, in the second control unit 26K, the polarity determination unit 26a determines the polarity of the ripple voltage value VRK and outputs a sign F_K of the polarity. The sign F_K has a value of +1 or −1. That is, the polarity determination unit 26a outputs the sign F_K having a value of +1 when the ripple voltage value VR_K is positive, and outputs the sign F_K having a value of −1 when the ripple voltage value VR_K is negative.

The first multiplier 26b calculates the ripple current value with polarity F_IRK by multiplying the ripple current value IR_K input from the output current ripple extraction unit 25K by the sign F_K input from the polarity determination unit 26a. The first multiplier 26b outputs the ripple current value with polarity FIR_K, which is a product of the ripple current value IR_K and the sign F_K, to the calculation unit 26c.

The calculation unit 26c calculates a difference between the ripple current value with polarity FIR_K input from the first multiplier 26b and a ripple target value set in advance, and outputs the difference to the PI control unit 26d. The ripple target value is a target value of a peak-to-peak current value of the output current ripple, and is set to 0 [App] in the present embodiment.

The PI control unit 26d performs proportional integral (PI) calculation based on the difference between the ripple current value with polarity FIR_K and the ripple target value, and generates a gain G_K for causing the ripple current value with polarity FIR_K to approach the target value. The PI control unit 26d also functions as a smoothing filter for rectification.

The second multiplier 26e multiplies the ripple voltage value VR_K input from the input voltage ripple extraction unit 24K by the gain G_L input from the PI control unit 26d to generate a second control command value FG_K that is a product of the ripple voltage value VR_K and the gain G_K.

The same applies to the second control units 26L and 26M. That is, the second control unit 26L generates a second control command value FG_L from the ripple voltage value VR_L input from the input voltage ripple extraction unit 24L and the ripple current value IR_L input from the output current ripple extraction unit 25L. Further, the second control unit 26M generates a second control command value FG_M from the ripple voltage value VR_M input from the input voltage ripple extraction unit 24M and the ripple current value IR_M input from the output current ripple extraction unit 25M.

The switching control unit 27 includes a calculation unit 27a and a pulse generation unit 27b. The switching control unit 27 performs feedforward control on the first control command value CC for bringing the output current value close to the target value using a second control command value FGx (x=K, L, or M) that is a product of the ripple voltage value VRx (x=K, L, or M) and the gain Gx (x=K, L, or M). Specifically, the calculation unit 27a adds the first control command value CC input from the PI control unit 23c and the second control command value FGx (x=K, L, or M) input from the second multiplier 26e, and outputs the addition value to the pulse generation unit 27b. The pulse generation unit 27b determines the driving frequency of the switching element of the primary-side switching circuit 21a on the basis of the addition value of the first control command value CC and the second control command value FGx, and generates a switching pulse for turning on/off the switching element at the driving frequency.

In the DC/DC converter 20′ according to the present embodiment, the control unit 22′ extracts the input voltage ripples of the Kth, Lth, and Mth order frequencies included in the input voltage, generates a current gain (gain Gx (x=K, L, or M)) for making the output current ripples of the Kth, Lth, and Mth order frequencies equal to or less than a predetermined value, and performs feedforward control on the input voltage ripples of the Kth, Lth, and Mth order frequencies by the current gain. Therefore, with the DC/DC converter 20′ according to the present embodiment, it is possible to more accurately reduce the output current ripple of the Kth, Lth, and Mth order frequencies.

Although the embodiments of the DC/DC converter and the power source device according to the present invention have been described above, the present invention is not limited to the embodiments.

The configuration of the DC/DC converter according to the present invention can be appropriately changed as long as the DC/DC converter includes a power unit that includes a drive circuit including a switching element and a rectifier circuit, switches an input voltage by the switching element, and rectifies the input voltage by the rectifier circuit to obtain a DC output, and a control unit that controls the drive circuit, in which the control unit includes a first control unit that generates a first control command value for bringing the output close to a target value, an input voltage ripple extraction unit that extracts an input voltage ripple included in the input voltage, an output ripple extraction unit that extracts an output ripple included in the output, a second control unit that calculates an output ripple with polarity by multiplying the output ripple by a value including polarity of the input voltage ripple, generates a gain for bringing the output ripple with polarity close to a ripple target value, and generates a second control command value by multiplying the input voltage ripple by the gain, and a switching control unit that performs feedforward control of the drive circuit on the basis of the first control command value and the second control command value.

For example, in the first embodiment, the second control unit 26 may include a gain-added polarity determination unit instead of the polarity determination unit 26a. The gain-added polarity determination unit performs gain adjustment of the ripple voltage value VR with a gain smaller than 1, and outputs the ripple voltage value VR′ after the gain adjustment to the first multiplier 26b. In this case, it is preferable to appropriately change the PI gain of the PI control unit 26d so that the PI control unit 26d can generate the gain G having the same value as that in the embodiment. In addition, the polarity determination unit 26a and the gain-added polarity determination unit may be eliminated, the ripple voltage value VR may be directly input to the first multiplier 26b, and the PI gain may be appropriately changed so that the output (gain G) of the PI control unit 26d falls within an allowable value. The same applies to the second embodiment.

In the second embodiment, the input voltage ripple extraction unit 24′ extracts the input voltage ripples of three frequencies (Kth, Lth, and Mth), but the input voltage ripples of the N number of frequencies (N is an integer equal to or more than 2) may be extracted. Similarly, the output current ripple extraction unit 25′ extracts output current ripples of three frequencies (Kth, Lth, and Mth), but may extract output current ripples of the N number of frequencies. The control unit 26′ may generate the N number of second control command values on the basis of the input voltage ripples of the N number of frequencies and the output current ripples of the N number of frequencies. The switching control unit 27 may perform feedforward control on the primary-side switching circuit 21a (drive circuit) on the basis of the first control command value and the N number of second control command values. That is, the control unit 22′ can be configured to cope with ripple noise of the N number of different frequencies.

In the first and second embodiments, the output current ripple has been described, but the same applies to an output voltage ripple and an output power ripple. For example, in a case of the output voltage ripple, the output voltage is detected by an output voltage detection unit instead of the output current detection in the output current detection unit 23a, and the output voltage ripple is extracted by an output voltage ripple extraction unit instead of extraction of the output current ripple in the output current ripple extraction unit 25.

The DC/DC converter according to the present invention may be a current resonant type DC/DC converter of a CLLC or CLLLC system capable of bidirectional operation, may be a current resonant type DC/DC converter of another system, may be a voltage current type DC/DC converter not having the resonance circuit 21b, or may be a DC/DC converter of a phase shift system, a dual active bridge (DAB) system, or the like. In addition, the pulse generation unit 27b of the first and second embodiments may output a switching pulse for PWM control or phase shift control instead of outputting a switching pulse for frequency modulation control. In addition, the DC/DC converter according to the present invention may be a non-isolated DC/DC converter that does not include the isolation transformer 21c.

In the control unit 22 of the first embodiment, for example, the output current detection unit 23a and the input voltage ripple extraction unit 24 may include an analog circuit, and the other units may include a digital circuit. In this case, the control unit 22 may perform A/D conversion processing on outputs of the output current detection unit 23a and the input voltage ripple extraction unit 24, read them by a digital circuit, perform software processing in the digital circuit, perform D/A conversion processing on the output of the pulse generation unit 27b, and output a switching pulse to the primary-side switching circuit 21a. The same applies to the second embodiment.

A power source device according to the present invention may include a plurality of DC/DC converters according to the present invention, or may include a plurality of power supply units including an AC/DC converter and a DC/DC converter according to the present invention.

DESCRIPTION OF REFERENCE SIGNS

• • 1, 1′ Power source device
  • 2 AC power supply
  • 3 Storage battery
  • 10 AC/DC converter
  • 20, 20′ DC/DC converter
  • 21 Power unit
  • 21a Primary-side switching circuit (drive circuit)
  • 21b Resonance circuit
  • 21c Isolation transformer
  • 21d Secondary-side rectifier circuit
  • 22, 22′ Control unit
  • 23 First control unit
  • 23a Output current detection unit
  • 23b Calculation unit
  • 23c PI control unit
  • 24, 24′ Input voltage ripple extraction unit
  • 25, 25′ Output current ripple extraction unit
  • 26, 26′ Second control unit
  • 26a Polarity determination unit
  • 26b First multiplier
  • 26c Calculation unit
  • 26d PI control unit
  • 26e Second multiplier
  • 27 Switching control unit
  • 27a Calculation unit
  • 27b Pulse generation unit